Single anchor mounting construction for brake shoes



Aug. 3, 1943. s. SCHNELL 2,325,998

SINGLE ANCHOR MOUNTING CONSTRUCTION FOR BRAKE SHOES Filed Dec. 22, 1941 INVENTOR EVE SOHNELL ATTORNEY Patented Aug. 3, 1943 SINGLE ANCHOR MOUNTING CONSTRUC- TION FOR BRAKE SHOES Steve Schnell, Kirkwood, Mo., assignor to Wagner Electric Corporation, St. Louis, Mo., a corpotion of Delaware Application December 22, 1941, Serial No. 423,897

11 Claims.

My invention relates to brakes and more particularly to an improved single anchor mounting construction for two shoes of an internal brake.

One of the objects of my invention is to provide an improved mounting for two brake shoes which embodies only a single anchor pin and permits both shoes to be self-centering under all conditions during braking.

Another object of my invention is to provide a single anchor pin mounting for two shoes which permits the anchored ends of the shoes to follow the drum outwardly when the latter expands during braking and to be automatically adjusted toward the drum to compensate for lining wear.

Still another object of my invention is to provide an improved single anchor mounting for the heel ends of two shoes which will be simple in construction, economical to manufacture and result in efficient braking action.

Other objects of my invention will become apparent from the following description taken in connection with the accompanying drawing in which Figure 1 is a side view of a two shoe brake assembly having a mounting for the shoes embodying my invention; Figure 2 is a sectional view taken on the line 2--2 of Figure 1; and Figure 3 is a view with parts broken away to show the curved abutment surfaces.

Referring in detail to Figures 1 and 2, the numeral l indicates the usual drum of the brake which is secured to a rotating member on a vehicle and 2 the fixed backing plate or support which closes the open side of the drum. Within the drum are positioned two brake shoes 3 and 4 comprising, respectively. webs 5 and 6, lining carrying flanges l and 8, and linings 9 and Ill. The toe ends of the shoes are adapted to be actuated into engagement with the drum by any suitable means, that shown comprising a hydraulic fluid motor ll embodying oppositely movable pistons I2 and I3, said pistons being moved by hydraulic pressure from a suitable source. The shoes are held in retracted position against stops l4 and It by a retracting spring l6 connected between the shoes.

The heel ends of the shoes are mounted upon the backing plate by my improved mounting means. This mounting means comprises a single anchor pin ll secured to the support 2 which is reinforced at this point by a plate I! (see Figure 2). Associated with the anchor pin are two abutment members l9 and 20 positioned on opposite sides of the anchor pin and lying in the same plane. The abutment member I! is formed with a partial circle recess 2| for engaging the 7 link is rotated on the anchor surface of the pin on one side of its axis and the abutment member 20 is provided with a partial circle recess 22 for engaging the surface of the pin on the other side of its axis. Each abutment member contacts less than degrees of the anchor pin surface. Thus it is seen that both abutment members are capable of rotative movement on the pin and about its axis. The abutment member I9 is provided with a curved surface 23 and the web of the heel end of shoe 3 has a similar curved surface 24 for cooperation with said curved surface 23. In a like manner the abutment member 20 has a curved surface 25 and cooperating therewith is a curved surface 26 on the web at the heel end of shoe 4.

Associated with the abutment member l9 and shoe 3- are two link 21 and 28 positioned on opposite sides of web 5 of said shoe. The abutment member 20 and shoe 4 also have associated therewith two links 29 and 30 positioned on opposite sides of the web of said shoe. The links 21 and 28, which lie on the same side of the webs of the shoes, are in overlapping relation with the link 21 On the inside adjacent the abutment member l9. The links 28 and 30 on the opposite sides of the webs of the shoes are also in overlapping relation with the link 30 adjacent the abutment member 20. All the links are provided with suitable openings for receiving the anchor pin. The link 21 is secured to the abutment member ill in any suitable manner, such as, for example, by welding and link 30 is secured in a like manner to the abutment member 20. Thus the abutment member i9 is moved with link 21 whenever this pin and abutment member 20 is rotated with link 30 whenever this link is rotated on the anchor pin.

The outer ends of links 27 and 28 are pivoted to web 5 of shoe 3 by a pin 8| passing through an oversized opening 32 in said web. Surrounding the pin is a rubber washer 33 of an external diameter to lit the opening 32. This washer in its normal shape has a uniform radial thickness but the opening 32 in the web of the shoe is so positioned with respect to pin 3| that when the shoe, the abutment member 19 and the links are assembled, the washer will be compressed so as to establish a force which causes the curved surface 24 on the end of shoe 3 to be held in pressure engagement with the curved surface 25 of the abutment member II. This pressure engagement establishes a frictional resistance to relative sliding movement between the curved surfaces. The curved surfaces have the same radius of curvature and the common axis thereof coincides with the axis of pin 3| which pivotally connects the links to the web of the shoe.

Links 29 and 34 are connected to web 8 of shoe 4 in the same manner as that described with respect to the connection of the links 21 and 28 to shoe 8. This construction comprises the pivot pin 34 passing through the oversized opening 35 in the web 8 of shoe 4 and the rubber washer 38 positioned in said opening 35 and surrounding the pin 34, said washer being compressed on one side when shoe 4. abutment member and links 29 and 30 are assembled in operative relation. The curved surfaces and 26 have their axis coinciding with the axis of pin 34.

All of the links and the abutment members i9 and 20 are maintained on the anchor pin by a c-washer 31, said anchor pin also having a flange 3B for holding the assembly away from the suport 2. p If the drum is rotating in the direction of the arrow, brake shoe 3 will act as a forward shoe and the brake shoe 4 as a reverse shoe when the fluid motor actuates the shoes into engagement with the drum. When the shoes are engaged with the drum, they will be rotated about the anchor pin i1 and there will be no relative movement between the curved surfaces 23 and 24 and 25 and 28 since during application, there will be no force sufficient to cause a sliding movement between these surfaces which are maintained 'in pressure engagement by the rubber washers. The links will act as part of each shoe in the same manner as if they were permanently secured to the shoe and pivoted on the anchor in. p When braking takes place there will be produced by shoe 3 a force which is indicated by the letter "N," said force acting directly on the curved surface of abutment member l8. This force N is the resultant of the circumferential force acting on the shoe and caused by the drag of the drum on the lining and a second downward force acting on the shoe. In order that the heel end of the shoe will have no tendency to move either toward or away from the drum during the braking action, this resultant force N should at all times be at right angles to a radial line of the drum center which passes through the point where said force is transferred to the abutment member ID. This is accomplished by the construction described as in such construction this radial line B will be tangent to the curved surfaces 28 and 24, the point of tangency coinciding with the point at which the force N acts. This relationship of the force N will always be the same at right angles to a radial line regardless of drum expansion due to heat or lining wear and throughout the working range of the brake shoe. Thus if there is an expansion of the brake drum. the shoe 3 will tend to move outwardly and follow the brake drum. Consequent- 1y, there will be a rotation of links 21 and Iii about the anchor pin i1 and a change in the axis of the curved surfaces 24 and 23. Also there will be some sliding movement between the curved surfaces as the shoe moves outwardly. This outward movement of the shoe will not, however, affect the relationship between the force N and a radial line drawn to the oint at which said force acts on the curved surface 23 of the abutment member 19. The direction of the forc N always remains thesame as the geometry or the brake does not change. Its position, however, is lower than that shown in Figure 1 due to is still, however, acting at right angles to a radial line of the brake assembly drawn through the point at which the force N acts on the curved surface 23. Since the mounting is such that this force N does not change its relationship with the center of the drum assembly, the shoe always centers itself and therefore is a self-centering brake shoe. Thus the brake shoe is perfectly controllable by the actuating means.

When lining wear takes place, the action is the same as when the drum expands, as shoe 3 will move outwardly and there will be a turning of the links relative to the shoe and a sliding between the curved surfaces. Any adjustment, however, due to lining wear will result in the adjustment being maintained due to the fact that the curved surfaces are in pressure engagement. When the adjustment takes place due to expansion of the drum there will be a re-adjustment when the drum contracts, this re-adjustment being caused by the wiping action of the drum as it contracts after the shoe is released. When the shoe is released, there will be no relative movement between the curved surfaces as the shoe, abutment member and links will pivot about the anchor pin as a unit. When the drum is rotating in the direction opposite that indicated by the arrow, then shoe 4 will become a forward shoe and its mounting will function. in the same manner as that of shoe 3.

When either one of the shoes acts as a reverse shoe, the only force tending to hold it into engagement with the drum is that produced by the fluid motor. If there is any expansion of the brake drum, the heel end of the shoe can adjust itself outwardly which will not be maintained when the drum contracts. However, if there is any adjustment due to lining wear, this adjustment will be maintained due to the fact that the curved surfaces are held in pressure engagement.

From the foregoing description it is apparent that I have devised a very simple and efllcient single anchor mounting for two brake shoes wherein either shoe will be a self-centering brake shoe when acting as a. forward shoe due to the mounting construction shown. The mountin construction is very compact and the forces acting on the anchor pin by both shoes are always in the same plane.

Being aware of the possibility of modifications in the particular structure herein described without departing from the fundamental principles of my invention, I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In braking mechanism, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for mounting said adjacent heel ends on the support, said mounting means comprising a single anchor nin, abutment members positioned for pivotal movement about the pin and lying in the same plane, said abutment members having curved surfaces for engagement by the curved surfaces on the heel ends of the shoes, a link non-rotatably connected to one abutment member and pivotally connected to the shoe engaged therewith, and a. second link non-rotatably connected to the other abutment member and pivotally connected to the shoe enthe fact that the shoe has moved outwardly. It 7 gaged therewith.

aaaaose 2. In braking mechanism, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adiacent heel ends, means for mounting said adiacent heel ends on the support, said mounting means comprising a single anchor pin, abutment members positioned for pivotal movement about the pin and lying in the same plane, said abutment members having curved surfaces for engagement by the curved surfaces on the shoe ends, a link non-rotatably connected to one abutment member and pivotally connected to the shoe engaged therewith, a second link non-rotatably connected to the other abutment member and pivotally connected to the shoe engaged therewith, and means for maintaining the cooperating curved surfaces of each shoe and its abutment member in pressure engagement.

3. In braking mechanism, a support, a brake drum, two b'rake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for mounting said adjacent heel ends on the support, said mounting means comprising a single anchor pin, abutment members positioned for pivotal movement about the pin and lying in the same plane, said abutment members having curved surfaces for engagement by the curved surfaces on the heel ends of the shoes, 9. link non-rotatably connected to one abutment member and pivotally connected to the shoe engaged therewith, a second link nonrotatably connected to the other abutment member and pivotally connected to the shoe engaged therewith, and a member of yieldable material associated with the pivotal connection of each link and shoe for biasing the curved end surface of the shoe into engagement with the cooperating curved surface on the engaged abutment memher.

4. In brakin mechansm, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for mounting said adjacent heel ends on the support, said mounting means comprising a single anchor pin, abutment members positioned on opposite sides of the pin in the same plane and having recessed portions engaging the pin surface for facilitating pivotal movement about the axis of the pin, each abutment member having a curved surface for engagement by a curved surface on the heel end of an adjacent shoe, a link secured to one side of one abutment member and pivotally connected to the same side of the shoe engaged therewith, and a second link secured to the other abutment member and pivotally connected to the shoe engaged therewith, said second link being positioned on the side of the said abutment and shoe opposite that of the first named link.

5. In braking mechanism, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for maintaining said adjacent heel ends on the support, said means comprising a single anchor pin, abutment members positioned on opposite sides of the pin in the same plane and having recessed portions engaging the pin surface for facilitating pivotal movement about the axis of the pin, each abutment member having a curved surface for engagement by a curved surface on the heel end of an adjacent shoe, a link secured to one side of one abutment member and pivotally connected to the same side of the shoe engaged therewith, a second link secured to the other abutment member and pivotally connected to the shoe n aged therewith, said second link being positioned on the side of the said abutment and shoe opposite that oi the first named link, and means between each link and the shoe to which it is pivoted for maintaining the curved end surface of the shoe in pressure engagement with the cooperating curved surface on the abutment. V

6. In braking mechanism, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for maintaining said adjacent heel ends on the support, said means comprising a single anchor pin, abutment members positioned on opposite sides of the pin in the same plane and having recessedmortions engaging the pin surface for facilitating pivotal movement about the axis of the pin, each abutment member having a curved surface for engagement by a curved surface on the heel end of an adjacent shoe, 9. link secured to one side of one abutment member and pivotally connected to the same side of the shoe engaged therewith, a second link secured to the other abutment member and pivotally connected to the shoe engaged therewith, said second link being positioned on the side of the said abutment and shoe opposite that of the first named link, and a rubber washer compressed between each link pivot pin and the shoe to which the link is pivoted for maintaining the curved end surface of the shoe in pressure engagement with the cooperating curved surface on the abutment.

7. In braking mechanism, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for mounting said adjacent heel ends on the support, said mounting means comprising a single anchor pin, abutment members positioned for pivotal movement about the pin axisand lying in the same plane, said abutment members having curved surfaces for engagement by the curved surfaces on the heel ends, two links pivotally connected to opposite sides of one shoe and also pivotally mounted on the anchor pin, one of said links being secured to the abutment member engaged by said shoe, and two links pivotally connected to opposite sides of the other shoe and also pivotally connected on the anchor pin, one of said links being secured to the abutment member engaged by said other shoe.

8. In braking mechanism, a support, a brake drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends, means for mounting said adjacent heel ends on the support, said mounting means comprising a single anchor pin, abutment members positioned for pivotal movement about the pin axis and lying in the same plane, said abutment members having curved surfaces for engagement by the curved surfaces on the heel ends, two links pivotally connected to opposite sides of one shoe and also pivotally mounted on the anchor pin, one of said links being secured to the abutment member engaged by said shoe, two links pivotally connected to opposite sides of the other shoe and also pivotally connected on the anchor pin, one of said links being secured to the abutment member engaged by said other shoe, and means for biasing the curved surface of each shoe end in pressure engagement with the surface with which it cooperates.

9. In braking mechanism, a support, a brake 4 s drum, two brake shoes positioned in the drum and provided with curved abutment surfaces on adjacent heel ends. means for mounting said adjacent heel ends on the support, said mounting means comprising a single anchor pin, abutment members positioned for pivotal movement about the pin axis and lying in the same plane. said abutment members having curved surfaces for engagement by the curved surfaces on the heel ends, two links pivotally connected to opposite sides of one shoe by a common pin and also pivotally mounted on the anchor pin, one of said links being secured to the abutment member engaged by said shoe, two links pivotally connected to opposite sides oi the other shoe by a common pin and also pivotally connected on the anchor pin, one of said links being secured to the abutment member engaged by said other shoe, and a rubber member so associated with each shoe pivot pin for the links that it will bias the shoe into pressure engagement with its abutment member.

10. In braking mechanism, a support, a brake drum, a brake shoe provided with a curved abutment surface on its heel end, means for mounting said heel end on the support, said mounting means comprising an anchor pin, an abutment member positioned i'or pivotal movement about the pin and having a curved surface for engagement by the curved surface on the heel end 01' the shoe, a link secured at one end to the abutment member and connected to the shoe by a pivot pin,-and a yieldable member compressed between the shoe and the link pivot pin for exerting a force maintaining the curved surfaces in pressure engagement.

11. In braking mechanism, a support, a brake drum, a brake shoe provided with a curved abutment surface on its heel end, means for mounting said heel end on the support, said mounting means comprising an anchor pin. an abutment member positioned for pivotal movement about the pin and having a curved surface for engagement by the curved surface on the heel end of the shoe, a link secured at one end to the abutment member and connected to the shoe by a pivot pin, and a rubber washer surrounding the link pivot pin and so compressed between the pin and shoe when the shoe, abutment member and link are assembled that it will cause the cooperating curved surfaces to be maintained in pressure engagement.

S'IEVE BCHNELL. 

